U.S. patent number 4,719,329 [Application Number 06/895,928] was granted by the patent office on 1988-01-12 for can body and method of making the same.
This patent grant is currently assigned to Toyo Seikan Kaisha, Limited. Invention is credited to Kazuhisa Ishibashi, Kazuma Kuse, Hiroshi Matsubayashi, Kenji Matsuno, Nobuyuki Sato.
United States Patent |
4,719,329 |
Matsuno , et al. |
January 12, 1988 |
Can body and method of making the same
Abstract
A can body of surface treated steel plate, such as TFS, having
adjacent longitudinally extending edges of tubular shaped member
welded by irradiation of laser beam and provided with inside
surface of welded seam having reliable paint retaining
characteristic and free from projections, such as upset. For the
purpose, welding is carried out such that inside and outside width
of molten-solidified zone and structure changed zone will be
maintained within a predetermined range and that metallic wire or
elongated backing strip is located oppositely to lower surface of
both edges being butt-welded.
Inventors: |
Matsuno; Kenji (Yokohama,
JP), Matsubayashi; Hiroshi (Kamakura, JP),
Ishibashi; Kazuhisa (Tokyo, JP), Kuse; Kazuma
(Yokohama, JP), Sato; Nobuyuki (Yokohama,
JP) |
Assignee: |
Toyo Seikan Kaisha, Limited
(Tokyo, JP)
|
Family
ID: |
15694427 |
Appl.
No.: |
06/895,928 |
Filed: |
August 13, 1986 |
Foreign Application Priority Data
|
|
|
|
|
Jul 7, 1986 [JP] |
|
|
61-159468 |
|
Current U.S.
Class: |
219/121.64;
219/160; 413/77 |
Current CPC
Class: |
B21D
51/2676 (20130101); B23K 26/262 (20151001); B23K
2103/04 (20180801) |
Current International
Class: |
B21D
51/26 (20060101); B23K 26/00 (20060101); B23K
26/26 (20060101); B23K 026/00 () |
Field of
Search: |
;413/74,77
;219/160,121LC,121LD |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Albritton; C. L.
Attorney, Agent or Firm: Meerkreebs; Samuel
Claims
What is claimed is:
1. A can body having a continuous laser-welded seam of adjacent
longitudinally extending edges of a tubular shaped member formed of
surface-treated, steel plate having 0.12-0.35 mm thickness wherein
an external width W1 and an internal width W2 of a
molten-solidified zone of the welded part will meet the requirement
specified by the formula W1.ltoreq.0.3 mm. and W1/5.ltoreq.W2 ,
characterized in that the height of a portion of the internal
surface of said welded part and adjacent area thereof projecting
from the internal surface of said tubular shaped member is
maintained less than 20 .mu.m,
2. A can body according to claim 1, wherein said internal width W2
of said molten-solidified zone is in a range of 0.06-0.23 mm.
3. A can body according to claim 1, wherein the width of the
heat-effected zone of said welded part is less than 0.5 mm.
4. The method of making a can body comprising the steps of:
A. supporting a surface-treated steel plate with longitudinally
extending edges thereof disposed in confronting relation to form a
tubular-shaped member; and
B. laser-beam welding said confronting, longitudinally extending
edge by applying the laser beam toward the external surface of the
steel plate while preventing leakage of the laser beam out of the
internal surface of the plate.
5. The method according to claim 4, wherein the preventing of
leakage of the laser beam is effected by positioning a metalic
backing strip beneath said confronting longitudinally extending
edges.
6. The method according to claim 5, wherein said tubular shaped
member is continuously conveyed in its longitudinal direction while
simultaneously continuously paying out said metalic backing
strip.
7. The method according to claim 5, wherein a magnetic force is
applied to said confronting longitudinally extending edges and
maintains them in alignment when welding is effected.
8. The method according to claim 7, wherein said magnetic force is
applied by means of a pair of roller-shaped permanent magnets, one
of each of said rollers being disposed beneath a respective one of
said longitudinally extending edges.
Description
The present invention relates to a can body and method of making
the same, more particularly a can body having continuous laser
welded seam of adjacent longitudinally extending edges of a tubular
shaped member formed of surface treated steel plate and method of
making the same.
DESCRIPTION OF PRIOR ART
U.S. Pat. No. 4,436,979 describes an undesirable slight weld upset
projecting outwardly from inside surface of tubular shaped member,
which is produced as a result of laser beam welding of adjacent
longitudinally extending edges of the same member.
Light from the laser beam passing through the weld joint area is
thought to produce this upset, which will unfavorably effect the
function and appearance of the weld. According to this U.S. Patent,
laser beam dump means is provided adjacent the welding area for
absorbing the light from laser beam produced by the laser welding
apparatus. However, the laser beam dump means will make it
difficult to locate an effective aligning means for both
longitudinally extending edges immediately below the weld joint
area.
PROBLEMS TO BE SOLVED BY THE PRESENT INVENTION
The present invention contemplates eliminating the weld upset
produced by the light from laser beam passing through the weld
joint area, to establish a limit of allowable size of the weld
upset produced on the internal surface of welded tubular member,
and to minimize vanishment or deterioration of the surface treated
layer of the blank, such as tin free steel, inevitably caused by
welding operation.
OBJECT OF INVENTION
An object of the present invention is to provide a can body of
surface treated steel plate having a longitudinal butt seam welded
by continuous laser beam irradiation, the inside surface of which
is enhanced in terms of corrosion resisting and film retaining
properties in the welded area.
A further object of the present invention is to provide a can body
and method of making the same, in which weld upset caused by light
of laser beam passing through the longitudinal butt seam weld area
is minimized.
An additional object of the present invention is to provide a can
body and method of making the same, in which alignment of both
longitudinally extending edges of tubular member is enhanced during
laser beam welding operation.
According to the present invention, there is provided a can body
having continuous laser welded seam of adjacent longitudinally
extending edges of tubular shaped member formed of surface treated
steel plate having 0.12.about.0.35 mm thickness, characterized in
that external width W1 and internal width W2 of molten-solidified
zone of welded part will meet requirement specified by following
formulae (1) and (2):
as illustrate in the accompanying drawing.
These and other objects, features and advantages of the present
invention will become more apparent from the following description
when taken in connection with the accompanying drawings, in
which:
IN THE DRAWING
FIG. 1 is a diagramatic cross sectional view showing a butt seam of
both longitudinally extending edges of a can body welded by laser
beam irradiation;
FIG. 2 is a cross sectional view showing a welding apparatus used
for the method according to the present invention;
FIG. 3 is a cross sectional view taken on the plane of line
III--III on FIG. 2;
FIG. 4a is a microscopic photograph showing a vertical section of a
welded part pf a can body taken perpendicularly to the direction of
welding, etched by a 5% nitric acid alcohol solution;
FIG. 4b is a microscopic photograph showing the same vertical
section as that of FIG. 4a etched by a 5% picric acid alcohol
solution;
FIG. 5 is a microscopic photograph showing a cross section of test
specimen No. 5, etched by a 5% nitric acid alcohol solution;
FIG. 6 is a magnified photographic picture taken by a scanning type
electronic microscope showing inside of the welded part of test
specimen No. 1; and
FIG. 7 is a magnified photographic picture taken by a scanning type
electronic microscope showing the inside of the welded part pf test
specimen No. 5.
DESCRIPTION OF PREFERRED EMBODIMENT(S)
Referring now to FIG. 1, the welded part comprises a
molten-solidified zone A defined by border lines x.sub.1, x.sub.2
on both sides, structure changed zones B1 and B2, that is, zones
each having steel structure changed in solid phase by heat
generated during welding operation, defined by border lines
(x.sub.1 y.sub.1) and (x.sub.2 y.sub.2) respectively and heat
effected zones C1 and C2, that is, zones having surface treated
layer deteriorated but the steel structure not affected by heat
generated during welding operation, each defined by border lines
(y.sub.1 z.sub.1) and (y.sub.2 z.sub.2). Area D located on the
outside of border lines z.sub.1, z.sub.2 is a normal area having no
change sustained in steel structure, nor in surface treated
layer.
In the case of welded can body made of tin free steel, the surface
treated layer d of normal area D comprises a layer of metallic
chromium and a layer of chromate laid over the former. Surface
layer c of the heat effected zone C consists a mixture of chrome
oxide, iron and iron oxide. Surface layer b of the structure
changed zone B and surface layer a of the molten-solidified zone A
consist a mixture of iron and iron oxide.
In case of the can body of tin plated steel plate, surface treated
layer d of the normal zone D comprises a layer of tin-iron alloy, a
layer of metallic tin laid over, and tin-iron alloy layer and a
layer of chromate laid over said metallic tin layer. Surface layer
c of the heat effected zone C1, C2 includes tin-iron alloy, iron
and iron oxide, some times a small amount of metallic tin. Surface
layer b of the structure changed zone B1, B2 and surface layer a of
the molten-solidified zone A consist iron and iron oxide, some
times a small amount of tin-iron alloy.
According to the present invention, in case internal width W4 of
the structure changed zone B1, B2 and internal width W6 of the heat
effected zone C1, C2 of the welded can body in preferable range in
desired, external width W1 and internal width W2 of the
molten-solidified zone A must meet the requirement W2.gtoreq.W1/5,
specified by formulae (1) and (2) described above. In this case,
internal width W4 of the structure changed zone B1, B2 of can body
of tin free steel will be, for instance, less than 0.25 mm and
internal width W6 of the heat effected zone C1, C2 will be less
than 0.5 mm.
In case of the can body of tin free steel, corrosion resisting
property of internal surface of the welded part is normally
inferior to that of non-welded portion of the can body having sound
surface layer of chromium related group preserved, even though the
welded portion having a surface layer of chromium related group
vanished or deteriorated by welding operation is repaired by some
kind of organic coatings. However, in case of the internal width W4
of structure changed zone B1, B2 and the internal width W6 of
heated effected zone C1, C2 being maintained in restricted range
according to the present invention, a can body having inside
coating of more than 3 .mu.m in average, preferably more than 5
.mu.m applied, is not inferior to any non-welded portion in terms
of corrosion resisting property and hence practically useful. The
reason for good corrosion resisting property of the welded portion
being maintained without decline will be a support presented to the
welded portion by adjacent non-welded portions on both sides to
keep the coating in clinging condition. The support will be
effectively extended since the width of deteriorated surface
treatment layer is considerably small.
In order to provide a laser welded can body meeting the requirement
specified by formulae (1) and (2) of the present invention, it is
necessary to make the size of laser beam irradiated on butt seam
smaller and a power density of the laser beam relatively
larger.
In the case of a small power density of laser beam, regardless of
the small size, a ratio W1/W2 of external width W1 to internal
width W2 and a value W1 will become larger, simultaneously internal
width W4 of the structure changed zone B1, B2 and the internal
width W6 of the heated effected zone will also become larger,
thereby affecting unfavourably to the corrosion resisting
property.
Shortage of the power density of laser beam will reduce a power per
unit volume of molten parts of the seam, extend the time required
for melting a metal irradiated by the laser beam, decrease a rate
of absorbtion of laser beam by non-molten part of the seam, and
render the time required for melting an inner surface prolonged.
For this reason, a welding speed will be lowered. Also, a
difference of temperature between molten part and adjacent area
will be reduced, thereby increasing a width of the heat effected
zone C1, C2.
Particularly, in case of tin free steel plate, the width of the
heat effected zone will be conspicuously enlarged, if the rate of
absorbtion of the laser beam is low and the power density of the
laser beam is small.
In case of a can body having molten-solidified zone A, external
width W1 and internal width W2 of which will meet the requirement
W2.gtoreq.W1/5 specified by formulae (1) and (2), heat conduction
from the above mentioned zone will be relatively small and the
internal width of the heat effected zone will become small, thereby
enabling the corrosion resisting property of welded part to become
enhanced. However, in case of the welded part having external width
W1 of molten-solidified zone A greater than 0.3 mm, a volume of
molten metal will become larger, with the heat conduction therefrom
increased, and the internal width of heat effected zone will be
enlarged, rendering a good corrosion resisting property difficult
to attain.
As described above, it is necessary to have a power density of the
laser beam irradiated on can body sufficiently great for securing a
welded part having a molten-solidified zone A, the external width
W1 and the internal width W2 of which will meet the requirement
W2.gtoreq.W1/5 specified by formulae (1) and (2). However, an
excessively great value of power density of the laser beam and
excessively low welding speed will cause the laser beam pass
through the welded part, and cause the inside surface of the welded
part to swell out, causing a molten metal to protrude out of border
lines between the molten-solidified zone A and structure changed
zone B1, B2 and solidify therearound irregularly, thereby producing
conspicuous irregularities extending in the direction of welding on
inside surface. These irregularities will make protective coatings
over protuberance thinner, sometimes exposing metallic surfaces and
make excessively heavy coatings in depressions, which will form
bubbles while baking, thereby causing the corrosion resisting
property of the welded part to decline. Also, conspicuous
protuberances will easily produce fractures when they are subjected
to bead-making operation or necking-in operation. According to the
present invention, a welded seam having substantially smooth inner
surface is provided by having a metallic wire pressed against inner
surface of butt seam in a position opposed to lower end of the
laser gun.
Referring to FIGS. 2 and 3, one embodiment of laser beam welding
apparatus 10 used for making a can body according to the present
invention is shown. The laser beam welding machine 10 comprises a
mandrel 2 inserted axially into a tubular shaped member 20 and a
laser gun 1 disposed above the tubular shaped member 20 adjacent to
right end of the mandrel 2. The mandrel 2 is provided with a Z-bar
3 mounted thereon in the upper part thereof, which has Z-shaped
cross section and extends parallel to the tubular shaped member 20.
The Z-bar 3 is provided with a pair of grooves (not shown)
receiving both longitudinally extending edges of the tubular shaped
member 20 and will bring both edges into aligned position on a same
circle immediately below the laser gun 1. The mandrel 2 is provided
at its right end with a roller 4 rotatably mounted thereon, which
is located opposite the lower end of the laser gun 1 with a pair of
adjacent longitudinally extending edges of the butt seam 14 held
between the lower end of the laser gun 1 and the roller 4. The
roller 4 will rotate about a shaft 12 and is provided with a
circumferential groove 8 for receiving the metallic wire 5. The
metallic wire 5 is inserted into the tubular shaped body 20 from
left end thereof, will pass around a guide roller 13, which is
located adjacent to right end of the mandrel 2, is led into a
direction shown by arrow head, fitted into the groove 8 provided
circumferentially in the roller 4, caused to pass nearly all around
the roller 4, and then is taken outwardly from left end of the
tubular shaped member 20. The metallic wire 5 is made of Aluminium
or Copper alloys thereof and will operate to intercept the laser
beam passing through the butt seam and debris of steel spread
thereby and to prevent swelling, such as upset, of molten metal.
Further, the metallic wire is in contact with inside surface of the
welded part and cool the same surface down by absorbing heat
therefrom. This cooling function will serve to suppress a tendency
of widening of the structure changed zone B1, B2 and the heat
effected zone C1, C2. The metallic wire 5 will also serve to
prevent oxidation of the welded part and adjacent area.
Alternatively, an elongated steel strip, such as backing strip or
chill strip, extending a considerable length along and maintained
in contact with inner surface of the welded part may be used,
instead of the metallic wire 5 passing around the roller 4.
As shown in FIG. 3, a pair of annular magnets 7 are mounted on the
roller 4 on both sides thereof and rotate together with the roller
4. Magnets 7 will attract both longitudinally extending edges
forming the butt seam 14 uniformly so as to maintain the same in
aligned position and prevent those edges from moving in
circumferential direction. The roller 4 is provided with a water
chamber 11 which is connected to suitable source of cooling water
(not shown). A plurality of spool-shaped guide rollers 6a, 6b, 6c,
. . . are disposed around the tubular shaped member 20 at uniform
spacing so as to direct the butt seam 14 to predetermined
position.
Another welding machine having same construction as that of the
machine described above, but without the metallic wire 5 and
provided with suitable support members of stainless steel for the
butt seam instead of a pair of magnets 7, 7, was constructed so as
to compare this welding machine with respect to the welding machine
shown in FIGS. 2 and 3 for comparison purpose. Outcome of the
testing showed that the welding machine of the present invention
will serve to reduce the value of W1, W2, W4, W6 more effectively
than the machine not utilizing the metallic wire 5 and magnets
7.
According to the present invention, a surface treated steel plate
having a thickness 0.12-0.35 mm is preferable. In case of the
thickness less than 0.12 mm, butt welding of high accuracy becomes
difficult for the reason of flexing and deformation due to heat of
the steel plate. On the other hand, in case of the surface treated
steel plate having thickness in excess of 0.35 mm, external width
W1 of the molten-solidified zone A exceeds 0.30 mm normally and
internal width W6 of the heat effected zone C1, C2 becomes greater,
thereby affecting unfavourably to corrosion resisting property.
A can body according to the present invention will have, for
instance, internal surface of main part D and heat effected zone
C1, C2 maintained on a cylindrical surface having a central axis
coincident with longitudinal axis of the tubular shaped member 20,
the internal width W4 of the structure changed zone B1, B2 is less
than 0.25 mm, and internal width W2 of the molten-solidified zone A
is 0.06.about.0.23 mm with external width Q1 maintained less than
0.3 mm. Further, a height of protuberance on inner surface of
molten-solidified zone A from a cylindrical surface, which is
concentric with the main part D and has same diameter as that of
the main part D, is maintained less than 20 .mu.m, and internal
surface of both molten-solidified zone A and structure changed zone
B1, B2 is substantially flush. Accordingly, in case of applying
protective coating on inside surface of welded part, there will be
no extremely thin coating even at protuberance, which will expose
metallic surface and decline the corrosion resisting property. In
case of the height of protuberance maintained less than 20 .mu.m,
there will be no fracture, nor any other flaw on the protective
coating which is subjected to neck-in or bead forming operation.
The internal width W6 of the heat effected zone C1, C2 is
maintained less than 0.5 mm.
EXAMPLE 1
A tin free steel plate, having thickness of 0.21 mm and provided
with metallic chromium layer having chromium density of 100
mg/m.sup.2 and chromate layer having chromium density of 10
mg/m.sup.2 laid over the former, was coated on the surface, which
is supposed to become inner surface of the can body, with paint of
epoxyi-phenol family, leaving the welded part and adjacent area
unpainted, and coated on the other surface too, and was severed
into blanks. This blank was shaped into tubular member with both
longitudinally extending edges abutted against each other, having
internal diameter of 65.3 mm and height of 104.7 mm.
Laser beam welding was carried out on this tubular member by using
the apparatus shown in FIGS. 2 and 3, with the size and power
density of laser beam and welding speed suitably selected. Internal
width W4 of the structure changed zone A determined from a metallic
structure, which was obtained by having a cross section of welded
part of the tubular member etched for 10 seconds by 5% nitric acid
alcohol solution, internal width W2, together with external width
Q1 of the molten-solidified zone A determined from the metallic
structure which was obtained by having a cross section of welded
part etched for 2 minutes by 5% picric acid alcohol solution, and a
height y of protuberance y on the inside surface of welded part are
shown in Table 1.
Microscopic photographs of metallic structure, which was obtained
by having a cross section perpendicular to direction of welding of
No. 1 test specimen etched by 5% nitric acid alcohol solution and
separately by 5% picric acid alcohol solution, are respectively
shown in FIG. 4a and FIG. 4b. In these photographs, A, B and D show
the molten-solidified zone, structure changed zone, and non-welded
zone respectively.
A photographic picture of microscopic structure, which was obtained
by having a longitudinal section of welded part of No. 5 test
specimen etched by 5% nitric acid alcohol solution, is shown in
FIG. 5. In this picture, Y shows a protuberance produced on the
inside surface of welded part. Microscopic photographs of internal
surface of welded part of No. 1 and No. 5 test specimen, which were
taken by using scanning type electronic camera, are shown
respectively in FIG. 6 and in FIG. 7.
Protective coating of epoxyi-phenol family was applied on the
welded part and adjacent area over approximately 5 mm width and
then baked. The thickness of coating was 8-10 .mu.m in average
after baking. Then, the can body was flanged at both ends. A can
end of tin free steel plate having inner surface thereof applied
with protective coating was double-seamed to the tubular member so
as to produce a container can body.
The can body was filled with cooked fish, and a lid of tin free
steel plate having inner surface applied with protective coating
was hermetically double-seamed to the open end, and thereafter
sterilized in retort for 90 minutes at a temperature of 116.degree.
C. This canned food was stored at 50.degree. C. for six months and
thereafter opened up to check up corroded condition of the inner
surface of welded part. Number of perforrations produced per 100
cans stored during 6 months was investigated and the outcome is
shown in Table 1.
Table 1 carries also various data of welded parts which were made
by the contrast machine lacking metallic wire 5 and ring-shaped
magnets 7.
EXAMPLE 2
A tin free steel plate, having a thickness of 0.18 mm and provided
with metallic chromium layer having chromium density of 100
mg/m.sup.2 and chromate layer having chromate density of 15
mg/m.sup.2, was applied on one surface, which is supposed to become
inner surface of the can body, with paint of epoxyi-phenol family,
with opposite surface being printed as desired, was severed into
blanks. Those blanks of tin free steel were shaped into tubular
members, and laser beam welding was carried out on those tubular
members under various conditions as shown in Table 2 by using a
welding machine shown in FIG. 2 and 3. Several welded can bodies
were made also by the contrast machine, similarly to the case in
Example 1.
The internal width W4 of the structure changed zone B1, B2
determined from a metallic structure, which was obtained by having
a cross section of welded part of the tubular member etched for 10
seconds by 5% nitric acid alcohol solution, and internal width W2,
together with external width W1 of the molten-solidified zone A
determined from the metallic structure which was obtained by having
a cross section of welded part etched for approximately 2 minutes
by 5% picric acid alcohol solution are shown in Table 2. And
maximum height y of protuberance on the inside surface of the
molten-solidified zone A is also shown in Table 2.
Protective coating of epoxyi-phenol family was applied on the
welded part over approximately 5 mm width, and then baked.
Thickness of protective coating was 8-10 .mu.m in average after
baking. The can body was flanged at both ends and then an end plate
of tin free steel plate having inside surface coated was
double-seamed to the can body.
The can body was filled with cooked fish, and a lid of tin free
steel plate having inner surface applied with protective coating
was hermetically double-seamed to the top end, and thereafter
sterilized in retort for 90 minutes at a temperature of 116.degree.
C. This canned food was stored at 50.degree. C. for six months and
thereafter opened up to check up corroded condition of the inner
surface of welded part. Number of perforations produced per 100
cans stored during 6 months was investigated, and the outcome is
shown in Table 2.
EXAMPLE 3
A tin plate, having a thickness of 0.23 mm and provided on one
surface with plated tin having a density of 2.8 g/m.sup.2, was
coated on one surface, which is to become inner surface of can
body, with paint of epoxyi-phenol family, leaving the to-be-welded
part and adjacent area unpainted, with the other surface suitably
coated, was severed into blanks.
In addition to tubular shaped members intended for regular testing
using the welding machine according to the present invention, extra
tubular shaped members intended for contrast welding machine have
been also prepared similarly to the case of Example 1.
The internal width W4 of the structure changed zone B1, B2,
internal width Q2 together with external width Q1 of the
molten-solidified zone A, and the height y of protuberance on the
internal surface of the molten-solidified zone A determined from
the metallic structure of cross-section of the welded part are
shown in Table 2.
Protective coating of epoxyi-phenol family was applied on the
inside surface of welded part and adjacent area over 5 mm width and
then baked. Thickness of protective coating after baking was 8-10
.mu.m in average. Then, a container can was made by providing
flanges at both ends and thereafter by double-seaming an end plate
of tin free steel plate having inside coating onto the tubular
shaped member.
The container can was filled with cooked fish. An end plate having
inside coating was hermetically double-seamed on open end of the
can body. The packed can was retort sterilized at 116.degree. C.
for 90 minutes, and stored at 50.degree. C. for six months, and
then opened to check up the corroded condition of inside surface of
welded part. And number of perforations produced per 100 cans
during 6 months period was also investigated. The outcome is shown
in Table 2. According to the present invention, adhesive property
and hence corrosion resisting property of protective coating
applied on the inside surface of the welded part after welding is
enhanced when carrying out laser beam welding on a butt seam of can
body.
TABLE 1
__________________________________________________________________________
EXAMPLE 1 MADE BY APPARATUS OF PRESENT INVENTION MADE BY CONTRAST
APPARATUS SPECIMEN NO. 1 2 3 4 5 6 7
__________________________________________________________________________
WELDING 12 15 10 10 12 12 8 SPEED m/min. LASER BEAM 0.20 0.16 0.16
0.20 0.20 0.20 0.22 DIAMETER mm LASER BEAM 1.0 1.0 0.80 1.0 1.0 0.3
1.0 POWER DENSITY kw W4 mm 0.21 0.15 0.10 0.24 0.27 0.40 0.42 W6 mm
0.38 0.30 0.30 0.40 0.42 0.80 0.75 W2 mm 0.20 0.10 0.07 0.22 0.23
0.10 0.30 W1 mm 0.29 0.20 0.25 0.30 0.30 0.35 0.35 y um 0 0 0 15 35
0 40 INSIDE NORMAL NORMAL NORMAL LOCAL CORROSION CORROSION
CORROSION CONDITION CORROSION ON ALL OVER ALL OVER SLIGHTLY
PROTUBERANCE PERFORATION 0 0 0 0 0 0 2
__________________________________________________________________________
TABLE 2
__________________________________________________________________________
EXAMPLE 2 EXAMPLE 3 SPECIMEN NO. 9 10 11 12
__________________________________________________________________________
APPARATUS USED APPARATUS OF CONTRAST APPARATUS OF CONTRAST PRESENT
INVENTION APPARATUS PRESENT INVENTION APPARATUS WELDING SPEED 18 18
15 15 m/min. LASER BEAM 0.16 0.16 0.16 0.16 DIAMETER mm LASER BEAM
1.0 1.0 1.0 1.0 POWER DENSITY kw W4 mm 0.12 0.20 0.15 0.20 W6 mm
0.25 0.30 0.30 0.35 W2 mm 0.09 0.11 0.12 0.13 W1 mm 0.20 0.17 0.23
0.20 y 0 35 0 30 INSIDE SURFACE NORMAL CORROSION ON NORMAL
CORROSION ON PROTUBERANCE PROTUBERANCE & ADJACENT AREA
PERFORATION 0 0 0 1
__________________________________________________________________________
* * * * *